1. Field of the Invention
The present invention relates to a fuel distributor included in a fuel feed system for automobiles.
2. Description of the Related Art
A fuel feed system for feeding fuel to an automotive engine pumps fuel through a fuel feed line to a fuel rail. The fuel is distributed to fuel injectors attached to the fuel rail to inject fuel into an intake manifold connected to the engine.
Referring to FIG. 5, a conventional fuel distributor has a fuel rail 10 formed by joining an upper case 10a and a lower case 10b, which are formed by pressing a plate. The joining parts of the upper case 10a and the lower case 10b are bonded together by brazing. Fuel injector cups 17 are attached to the lower wall of the lower case 10b. The terminal end of a fuel feed pipe 12 is connected to a middle part of the upper wall of the upper case 10a. If there is a spatial restriction on laying the fuel feed pipe 12, the terminal end of the fuel feed pipe 12 is connected to a side wall of the upper case 10a as shown in FIG. 6.
Problems with the fuel distributor include the pulsation of fuel due to the fuel-injecting operation of the fuel injectors, and the transmission of noise by the fuel rail. It has been a usual practice to attach an outer damper to the fuel rail to suppress vibrations and noise transmission. It is a recent technical trend to provide the fuel rail with an internal damping means or to design the three-dimensional shape of the fuel rail so that the fuel rail may absorb vibrations and noise.
To provide the fuel rail with a pulsation suppressing function and a noise transmission suppressing function, it is advantageous to the fuel rail that the fuel rail is designed in a shape deformable according to pressure variation to absorb vibrations and noise easily. However, it is delicate and difficult to design the fuel rail so that the fuel rail meets both a requirement for rigidity and a requirement for vibration/noise absorption. Fuel rails of some fuel-distributing units are satisfactory in effect on pulsation suppression and unsatisfactory in effect on noise transmission suppression and vice versa. Thus, it is difficult to provide a fuel rail capable of coping with both pulsation suppression and noise transmission suppression at the present.